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The absolute magnitudes of RR Lyrae stars - II. DX Delphini.
Jameson, R. F.; Fernley, J. A.; Lynas-Gray, A. E. +2 more
UV, IR and visual photometry of the short-period RR Lyrae star DX Del is presented and treated by means of the Blackwell and Shallis (1977) IR Flux Method-based formulation of the Baade-Wesselink method. Upon correcting to common reddening, extinction, and radial-velocity conversion factors, as well as applying the Baade-Wesselink analysis of Burk…
A 2597 : another massive cooling flow.
Fabian, A. C.; Johnstone, R. M.; Crawford, C. S. +1 more
We present X-ray, optical and ultraviolet observations of the rich cluster A2597 and confirm the presence of a central cooling flow. The intracluster gas is cooling at a rate of ~370 M_sun_ yr^-1^ and we observe extended optical line-emitting gas around the central galaxy over a radial distance of ~25 kpc. Examination of the blue continuum spectru…
A 4.1 keV spectral feature in a type 1 X-ray burst from EXO 1747-214.
van Paradijs, J.; Lewin, W. H. G.; Magnier, E. +3 more
We present the results of a spectral analysis of two type 1 bursts from EXO 1747-214 detected during 9.4 h of observing with EXOSAT. The spectrum, during the rise of the strongest burst, shows a spectral feature, which can be well represented by an absorption line at 4.05 +/- 0.1 keV; the line has an equivalent width of 570 +/- 87 eV; the upper li…
The X-ray spectrum of QSO 1821+643.
Barstow, M. A.; Warwick, R. S.; Yaqoob, T.
Pravdo & Marshall have reported an unusually soft X-ray spectrum for the high-luminosity QSO 1821 + 643, based on measurements from the A2 experiment on HEAO-1. However, in a series of EXOSAT observations of this object we have found the medium-energy X-ray spectrum to be consistent with the canonical form observed in low-luminosity active gal…
Broad emission line variability in 3C 273.
Zheng, W.; Wilson, R.; O'Brien, P. T.
We find that the broad Ly α H{BETA} and Fe II emission lines in the luminosity quasar 3C 273 vary by 10-30 per cent on time-scales less than a year. All the line variations occurred during approximately the same period. The line cores vary more than the wings, indicating that the line variability involves only pan of the BLR. The line variability …
The 2.8-hour flux modulation of the cataclysmic variable PG 1711+336.
Branduardi-Raymont, G.; Mason, K. O.; Rosen, S. R. +1 more
High-speed optical photometry of the cataclysmic variable PG1711 + 336 is used to confirm the presence of a 2.8-hour periodic modulation in the light curve of the star and to improve its ephemeris. Pronounced flickering on time-scales between 10 and 20 minutes is found superimposed on the 2.8-hour variation. Three hours of time-resolved spectrosco…
Non-Planckian behaviour of burst spectra : dependence of the blackbodyradius on the duration of bursts.
van Paradijs, J.; Jansen, F.; Oosterbroek, T. +3 more
Exosat observations indicate a strong correlation between X-ray burst duration and the blackbody temperature measured at the moment when the flux has decayed to 10 percent of the Eddington flux. No correlation is observed between the persistent flux near the burst and this temperature. Burst spectra reveal deviations from a Planckian spectrum whic…
IUE archive observations of dwarf nova WZ SGE during outburst.
Naylor, T.
Observations from the International Ultraviolet Explorer archive are used to show that during the 1978 outburst of the dwarf nova WZ Sge, its orbital light curve displayed dips, similar to those seen during the outbursts of other high-inclination dwarf novae. These dips are thought to be due to obscuration of the inner regions of the accretion dis…
Discovery of a BL Lacertae object (EXO 055625-3838.6) in the error box of H 0557-385.
Tagliaferri, G.; Beuermann, K.; Giommi, P. +3 more
We present X-ray and optical data of a new BL Lacertae type object (EXO 055625-3838.6) which has been serendipitously discovered in an EXOSAT CMA image and is located within the error box of HO557-385 (4U0557-38, 3A0557-383), a hard X-ray source previously identified with a seyfert 1 galaxy. Although the soft X-ray flux of the BL Lac is 1O times h…
High-resolution Hα spectroscopy of the bright RS CVn system HR 7275.
Eker, Zeki
HR 7275 is a bright, long-period (28 day), single-lined RS CVn binary. High-resolution (0.36 A) and good signal-to-noise ratio echelle spectra do not show any clear evidence of the secondary in the system on spectral lines. Also, absence of a continuum on a low-resolution UV spectrum (IUE merged log) and the known mass function imply a main-sequen…